Each Wednesday the USAMU offers tips for handloaders on the USAMU Facebook page. This article from the “Handloading Hump-Day” archives should interest pistol competitors, an any shooter who enjoys getting the best possible accuracy from their fine pistols. In this article, the USAMU’s experts share key tips that can help optimize your pistol ammo. Follow this tips to produce more consistent ammo, that can shoot higher scores.
Optimize the Taper Crimp
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of crimp and its effect on accuracy. Different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors. It is not unusual for our Shop to vary a load’s crimp in degrees of 0.001″ and re-test for finest accuracy.
Use Consistent Brass
Brass is also important to pistol accuracy. While accurate ammunition can be loaded using brass of mixed parentage, that is not conducive to finest results, particularly at 50 yards. It is important for the serious competitor/handloader to use brass of the same headstamp and ideally one lot number, to maximize uniformity. Given the volumes of ammunition consumed by active pistol competitors, using inexpensive, mixed surplus brass for practice, particularly at the “short line” (25 yards), is understandable. However, for the “long line” (50 yards), purchasing and segregating a lot of high-quality brass to be used strictly for slow-fire is a wise idea.
Importance of Uniform COAL
Uniformity of the Case Overall Length (COAL) as it comes from the factory is also important to achieving utmost accuracy. More uniform case lengths (best measured after sizing) contribute to greater consistency of crimp, neck tension, ignition/burn of powder charge, and so on. Cartridge case-length consistency varies from lot to lot, as well as by maker. Some manufacturers are more consistent in this dimension than others. [Editor’s note: It is easy to trim pistol brass to uniform length. Doing this will make your taper crimps much more consistent.]
Primers and Powders — Comparison Test for Accuracy
Pay attention to primer brands, powder types and charges. Evaluating accuracy with a Ransom or other machine rest at 50 yards can quickly reveal the effect of changes made to handload recipes.
Bullet Selection — FMJ vs. JHP
Bullets are another vital issue. First, there is the question of FMJ vs. JHP. A friend of this writer spent decades making and accuracy-testing rifle and pistol bullets during QC for a major bullet manufacturer. In his experience, making highly-accurate FMJ bullets is much more difficult than making highly-accurate JHPs, in large part due to the way the jackets are formed. Small die changes could affect accuracy of FMJ lots dramatically.
The CMP now allows “safe, jacketed ammunition” in Excellence-in-Competition (EIC) Service Pistol matches, although wadcutter ammunition is prohibited. Thus, the option to use very accurate JHP designs simplifies the life of CMP Service Pistol shooters in pursuit of the prestigious Distinguished Pistol Shot badge.
Hopefully, these tips will be helpful to any pistol shooters interested in accurate handloads, not just “Bullseye” shooters. Small tweaks to one’s normal routine can pay big dividends in improved accuracy and make practice and competition more rewarding.
Stay safe, and good shooting!
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It’s not easy to place a first shot on target at 1500 yards. You must measure the wind speed with precision, know your exact muzzle velocity, and have a sophisticated ballistics solver. In this short video from Ryansrangereport.com, the shooter manages a first-round hit on a steel silhouette at 1500 yards. He used a Kestrel 4500 NV Weather Meter with Applied Ballistics software to figure out the trajectory for his 6.5 Creemoor rounds.
The Kestrel recorded a wind velocity, and the internal software calculated a solution of 17 Mils elevation (that’s 928 inches of drop) with 2.5 Mils windage. “Bang” — the shooter sends it, and 2.6 seconds later “Clang” he had a hit (flight time was 2.6 seconds). Bryan Litz observes: “This is the science of accuracy (in the form of an Applied Ballistics Kestrel) being put to good use at 1500 yards”.
Later in the video (1:05-1:15) the shooter places three rounds on steel at 1000 yards in just 10 seconds. The three shots all fall within 10″ or so — pretty impressive for rapid fire. The shooter reports: “[In my 6.5 Creedmoor] I’m using a 136gr Lapua Scenar L. This bullet has impressed me. It screams out of my barrel at 2940 fps and holds on all the way out to 1,500 yards.”
The rifle was built by Aaron Roberts of Roberts Precision Rifles (RPRifles.com). Chambered for the 6.5 Creedmoor, it features a Leupold Mark VI 3-18x44mm scope.
The .22 Long Rifle (.22 LR) round is widely regarded as a relatively weak cartridge with very little penetrating power. Compared to most centerfire ammo that’s certainly true. But the venerable .22 LR actually packs more punch than you might expect. A recent test by rimfire specialist 22Plinkster demonstrated that the little .22 LR has enough power to drive a bullet through multiple walls.
In this video, 22Plinkster tests two types of .22 Long Rifle ammo, seeing how far a .22 LR bullet will pass through sheets of 1/2″-thick drywall. He shoots CCI Velocitor and CCI Stinger ammo types from both a pistol and a rifle. The results may surprise you. Shot from a pistol, the CCI Stinger ammo penetrated Nine (9) drywall sheets. Out of the rifle, the CCI Velocitor Ammo passed through Eleven (11) sheets, while the CCI Stinger stuck in the eleventh board, after passing through Ten (10) sheets.
The rimfire ammo’s penetrating power surprised .22 Plinkster: “I was really surprised that [the ammo] went through as many [dry wall boards] as it did. I was thinking four, maybe five tops …” He points out that the rifle penetration of 11 sheets was “equivalent to five walls, maybe six walls. If you were shooting in your house, and you had 1/2″ drywall, it would go through five walls. Now, that’s pretty scary that a .22 Long Rifle could do that.”
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We know many of our readers aren’t 100% clear on the difference between a secant ogive bullet and a tangent ogive bullet. Add the “blended” or “hybrid” ogive into the design equation and you add to the confusion. In this article, Berger Ballistician Bryan Litz, explains the characteristics of the three popular ogive types: tangent, secant, and hybrid.
In discussions of ballistics, you’ll see references to “tangent” and “secant” bullet shapes. For many readers, these terms can be confusing. To add to the confusion, bullet makers don’t always identify their projectiles as secant or tangent designs. This article provides a basic explanation of tangent and secant designs, to help you understand the characteristics of both bullet shapes.
Tangent vs. Secant vs. Hybrid
Most match bullets produced today use a tangent ogive profile, but the modern VLD-style bullets employ a secant profile. To further complicate matters, the latest generation of “Hybrid” projectiles from Berger Bullets feature a blended secant + tangent profile to combine the best qualities of both nose shapes. The secant section provides reduced drag, while the tangent section makes the bullet easier to tune, i.e. less sensitive to bullet seating depth position.
Berger Bullets ballistician Bryan Litz explains tangent and secant bullet ogive designs in a glossary section of his Applied Ballistics website, which we reprint below. Bryan then explains how tangent and secant profiles can be combined in a “hybrid” design.
How Bullet Ogive Curves are Defined
While the term “ogive” is often used to describe the particular point on the bullet where the curve reaches full bullet diameter, in fact the “ogive” properly refers to the entire curve of the bullet from the tip to the full-diameter straight section — the shank. Understanding then, that the ogive is a curve, how is that curve described?
LITZ: The ogive of a bullet is usually characterized by the length of its radius. This radius is often given in calibers instead of inches. For example, an 8 ogive 6mm bullet has an ogive that is a segment of a circular arc with a radius of 8*.243 = 1.952”. A .30-caliber bullet with an 8 ogive will be proportionally the same as the 8 ogive 6mm bullet, but the actual radius will be 2.464” for the .30 caliber bullet.
For a given nose length, if an ogive is perfectly tangent, it will have a very specific radius. Any radius longer than that will cause the ogive to be secant. Secant ogives can range from very mild (short radius) to very aggressive (long radius). The drag of a secant ogive is minimized when its radius is twice as long as a tangent ogive radius. In other words, if a tangent ogive has an 8 caliber radius, then the longest practical secant ogive radius is 16 calibers long for a given nose length.”
Ogive Metrics and Rt/R Ratio
LITZ: There is a number that’s used to quantify how secant an ogive is. The metric is known as the Rt/R ratio and it’s the ratio of the tangent ogive radius to the actual ogive radius for a given bullet. In the above example, the 16 caliber ogive would have an Rt/R ratio of 0.5. The number 0.5 is therefore the lowest practical value for the Rt/R ratio, and represents the minimum drag ogive for a given length. An ogive that’s perfectly tangent will have an Rt/R ratio of 1.0. Most ogives are in between an Rt/R of 1.0 and 0.5. The dimensioned drawings at the end of my Applied Ballistics book provide the bullets ogive radius in calibers, as well as the Rt/R ratio. In short, the Rt/R ratio is simply a measure of how secant an ogive is. 1.0 is not secant at all, 0.5 is as secant as it gets.
Hybrid Bullet Design — Best of Both Worlds?
Bryan Litz has developed a number of modern “Hybrid” design bullets for Berger. The objective of Bryan’s design work has been to achieve a very low drag design that is also “not finicky”. Normal (non-hybrid) secant designs, such as the Berger 105gr VLD, deliver very impressive BC values, but the bullets can be sensitive to seating depth. Montana’s Tom Mousel has set world records with the Berger 105gr VLD in his 6mm Dasher, but he tells us “seating depth is critical to the best accuracy”. Tom says a mere .003″ seating depth change “makes a difference”. In an effort to produce more forgiving high-BC bullets, Bryan Litz developed the hybrid tangent/secant bullet shape.
Bryan Litz Explains Hybrid Design and Optimal Hybrid Seating Depths
Story sourced by Edlongrange.
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Shiny brass — it may not shoot more accurately, but it does make you feel better about your hand-loaded ammo. While it’s not necessary to get brass “bright and shiny” after every firing, it is a good idea to clean powder residue, grime, and grit off your brass before you run cases into sizing dies. There are many ways to clean cartridge cases. A quick wipe with solvent on a patch may suffice for recently-shot cases. Older brass with baked-on carbon may require lengthy tumbling. Ultrasonic cleaning is another popular option that gets your brass clean inside and out.
Sinclair International has a series of helpful videos on brass cleaning. These short “how-to” videos, hosted by Bill Gravatt, Sinclair’s past President, cover the various processes you can use — tumbling, ultrasonic cleaning, chemical cleaning, and cleaning by hand.
Video ONE — Cleaning Brass in Vibratory or Rotary Tumbler
TIP: Brass that has recently been shot will clean more easily than brass that has been sitting many days or weeks. If your tumbling media is fresh the job should be done in an hour or less. It’s your choice whether to tumble with primers removed or with primers still in the cases. If you choose to tumble with primers out, we suggest you deprime with a depriming die, rather that put dirty brass into your sizing die. Some people like to add a teaspoon of liquid polish to the media. This does work, cutting tumble time, and making your brass more shiny. However, if you add liquid polish, do that BEFORE you add the brass and let the tumbler run for a 15 minutes to get the polish completely mixed into the media. Otherwise you can else up with gooey gunk inside your cases — a very bad thing.
Video TWO — Ulstrasonic Case Cleaning
TIP: There are many different types of solutions you can use. Soapy water suffices for some folks, particularly if you add a little Lemi-Shine. The Hornady and Lyman solutions work well, and can be used multiple times, provided you strain the solution to remove dirt and grit after cleaning sessions. Many ultrasonic cleaning machines have timers. Experiment with dwell time to see how long you need to immerse your brass. A very small amount of Ballistol in the solution will help lubricate your necks on the inside. This can make bullet seating go more smoothly, with more consistent neck tension.
Video THREE — Chemical Cleaners (Soaking without Ultrasound)
TIP: After using chemical cleaners, such as the Iosso solution, you need to water-rinse your brass thoroughly. A kitchen strainer helps with this (see video at 0:20). Also, don’t forget your brass in the chemical solution — follow the manufacturers recommendations and don’t exceed the recommended dwell time. Chemical cleaners work surprisingly well to remove grease and grime, and the solution can be re-used multiple times. However, if you want your cases to look bright and shiny (like new brass), you will probably have to tumble. [Editor: A very effective new chemical cleaner is the Brass Monkey product from the makers of Wipe-Out and Carb-Out. Add a teaspoon to a gallon of water then soak your brass for 20-30 minutes. It really works — the cases clean up dramatically].
Video FOUR — Manual Cleaning (By Hand)
TIP: Keep some oversize patches in your range kit. At the end of your shooting sessions, wipe off your fired brass with a patch dampened with a mild, non-corrosive solvent (once again Ballistol works well). Before the carbon sets up on your brass it is very easy to remove. For tougher jobs, you can use 0000 Steel Wool (as Bill recommends in the video). You may find that timely hand-cleaning lets you avoid tumbling altogether — or you may choose to tumble (or ultra-sound) your brass only after a half-dozen or so firings.
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The wait is over… Creedmoor Sports is now producing some of the best .223 Rem target ammo you can buy. Three “match-grade” types are offered with Sierra bullets and NEW Lake City cartridge brass. If you shoot Service Rifle, you may find that this new Creedmoor ammo rivals good handloads — and that’s quite an achievement. Creedmoor General Manager Dennis DeMille, a past National Service Rifle Champion, states: “As a National Rifle Champion and having fired probably a Gazillion rounds down range (mostly hand loads), I would not hesitate to compete with this ammunition on a National Level!”
Creedmoor currently offers .223 Rem competition ammo loaded with three of the most popular projectiles: 69 grain Sierra TMK (Tipped MatchKing), the 77 grain Sierra TMK, and the 77 grain Sierra BTHP. All three ammo types are loaded in Creedmoor’s new production facility using brand new Lake City Brass. As with all Creedmoor Ammo, each lot is pressure tested and velocity tested prior to every round being hand-inspected and packaged. That gives you confidence that this ammo is consistent lot to lot. Given the quality of this ammo, it is VERY affordable, starting at $34.75 per 50-round box. That works out to $0.69 per round. At that price, when you consider hand-loading, you have to ask yourself “what’s your time worth”? Would that time be better spend practicing?
Quantity Discounts and FREE Shipping on Large Orders
Creedmoor offers quantity discounts on the .223 Rem ammo: “Order Five (5) or more boxes of any one round to get your first price break. Order Ten (10) boxes of ANY combination of Creedmoor Ammo (Rifle or Pistol, Mix and Match) you get free shipping.”
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There’s an all-new book from Applied Ballistics. Modern Advancements in Long Range Shooting – Volume II, is now available for pre-order from the Applied Ballistics eStore. This 356-page hardcover resource is chock full of information, much of it derived through sophisticated field testing. The pre-order price is $34.95, $5.00 off the regular $39.95 price. The books are expected to ship in July, 2016.
AUDIO FILE: Bryan Litz Talks about Modern Advancements in Long Range Shooting, Volume 2. (Sound file loads when you click button).
Volume II of Modern Advancements in Long Range Shooting contains all-new content derived from research by Applied Ballistics. Author Bryan Litz along with contributing authors Nick Vitalbo and Cal Zant use the scientific method and careful testing to answer important questions faced by long range shooters. In particular, this volume explores the subject of bullet dispersion including group convergence. Advanced hand-loading subjects are covered such as: bullet pointing and trimming, powder measurement, flash hole deburring, neck tension, and fill ratio. Each topic is explored with extensive live fire testing, and the resulting information helps to guide hand loaders in a deliberate path to success. The current bullet library of measured G1 and G7 ballistic coefficients is included as an appendix. This library currently has data on 533 bullets in common use by long range shooters.
Bryan tells us that one purpose of this book is to dispel myths and correct commonly-held misconceptions: “Modern Advancements in Long Range Shooting aims to end the misinformation which is so prevalent in long range shooting. By applying the scientific method and taking a Myth Buster approach, the state of the art is advanced….”
Bullet Dispersion and Group Convergence
Part 1 of this Volume is focused on the details of rifle bullet dispersion. Chapter 1 builds a discussion of dispersion and precision that every shooter will benefit from in terms of understanding how it impacts their particular shooting application. How many shots should you shoot in a group? What kind of 5-shot 100 yard groups correlate to average or winning precision levels in 1000 yard F-Class shooting?
Chapter 2 presents a very detailed investigation of the mysterious concept of group convergence, which is the common idea that some guns can shoot smaller (MOA) groups at longer ranges. This concept is thoroughly tested with extensive live fire, and the results answer a very important question that has baffled shooters for many generations.
Part 2 of this Volume is focused on various aspects of advanced hand-loading. Modern Advancements (Vol. II) employs live fire testing to answer the important questions that precision hand loaders are asking. What are the best ways to achieve MVs with low ES and SD? Do flash hole deburring, neck tension, primer selection, and fill ratio and powder scales sensitivity make a difference and how much? All of these questions are explored in detail with a clear explanation of test results.
One of the important chapters of Part 2 examines bullet pointing and trimming. Applied Ballistics tested 39 different bullet types from .224 through .338 caliber. Ten samples of each bullet were tested for BC in each of the following configurations: original out of the box, pointed, trimmed, pointed and trimmed. The effect on the average BC as well as the uniformity in BC was measured and tabulated, revealing what works best.
Part 3 covers a variety of general research topics. Contributing author Nick Vitalbo, a laser technology expert, tested 22 different laser rangefinders. Nick’s material on rangefinder performance is a landmark piece of work. Nick shows how shooters can determine the performance of a rangefinder under various lighting conditions, target sizes, and reflectivities.
Chapter 9 is a thorough analysis of rimfire ammunition. Ballistic Performance of Rifle Bullets, 2nd Edition presented live fire data on 95 different types of .22 rimfire ammunition, each tested in five different barrels having various lengths and twist rates. Where that book just presented the data, Chapter 9 of this book offers detailed analysis of all the test results and shows what properties of rimfire ammunition are favorable, and how the BCs, muzzle velocities and consistency of the ammo are affected by the different barrels.
Chapter 10 is a discussion of aerodynamic drag as it relates to ballistic trajectory modeling. You will learn from the ground up: what an aerodynamic drag model is, how it’s measure and used to predict trajectories. Analysis is presented which shows how the best trajectory models compare to actual measured drop in the real world.
Finally, contributing author Cal Zant of the Precision Rifle Blog presents a study of modern carbon fiber-wrapped barrels in Chapter 11. The science and technology of these modern rifle barrels is discussed, and then everything from point of impact shift to group sizes are compared for several samples of each type of barrel including standard steel barrels.
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Ever wonder how (and where) Sierra tests its bullets? The answer is underground, in a 300-meter test tunnel located under Sierra’s factory in Sedalia, Missouri. The photo above shows the construction of the tunnel back in May, 1990. Like most bullet manufacturers, Sierra does live-fire bullet testing to ensure that Sierra projectiles perform as promised, with repeatable accuracy. Sierra’s 300-meter test range is the longest, privately-owned underground bullet test facility in the world. Sierra offers free tours of the test tunnel as part of Sierra’s Factory Tour Program.
Sierra Bullets tests every new bullet design and each lot of bullets. Sierra tells us: “When [we] change to a new bullet they are continually shooting them until they get the bullet properly set up and running and the range releases them to run (meaning the bullets shoot to spec). [Testers] are required to shoot at any lot change and periodically throughout the lot … even if it is just a press operator change. Lot sizes can vary from 5,000 to over 100,000 thousand. If anything changes — it is a new lot. When a new operator comes on — it is a new lot.”
Bevy of Barreled Actions for Bullet Testing
Sierra Bullets uses dozens of barreled actions for testing bullets. These barreled actions are clamped in stout, return-to-battery test fixtures. These heavy test fixtures provide near-perfect repeatability (with no human-induced holding or aiming errors). Each barrel has its own logbook to track the barrel’s usage. Interestingly, Sierra does not have a specific round count for barrel life. When a barrel starts “opening up”, i.e. showing a decline in accuracy, then the barrel is replaced, whether it has 800 rounds through it or 5,000.
Click Photo to Zoom
Sierra Bullets 10-Shot Groups at 200 yards
What kind of 200-yard accuracy can you get in an enclosed, underground test range? Would you believe 0.162 MOA at 200 yards with a .338? Check out these 10-shot test groups shot at the Sierra Test Range at 200 yards. Note that the numbers listed on each sample are actual measurements in inches. To convert to MOA, cut those numbers in half (to be more precise, divide by 2.094, which is 1 MOA at 200 yards). For example, the 0.340″ middle group works out to 0.162 MOA at 200 yards.
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Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
At the request of our readers, we provide select “Deals of the Week”. Every Monday morning we offer our Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.
1. Natchez — Special 5 Reloading Press Kit, $199.99
This is an excellent entry-level reloading kit, which is on sale for $199.99 at Natchez Shooters Supply. We like the relatively compact Special 5 press for most reloading duties. Eventually you many want to add an additional large heavy press, but this will get the job done. This kit includes an RCBS Powder Measure, Digital Scale, Powder Trickler, Hand Priming Tool, Load Manual, Loading Tray, and more. It’s hard to beat this combination of tools for under $200.00.
2. CDNN Sports — Remington 597 for $149.99
Looking for a “first rifle” for a family member? Consider this semi-auto Remington 597. It currently retails for just $149.99. That’s right, for under $150 you can get a reliable, self-feeding rimfire rifle that will provide years of fun for a young shooter. The 597 has a stock that’s sized right for both youngsters and adults. Receivers are dovetailed for standard rimfire rings and are also drilled and tapped to allow mounting of Weaver-style bases.
3. Grafs.com — Forster Co-Ax Reloading Press on SALE
If you’ve been patiently waiting to acquire a Forster Co-Ax® reloading press, now’s the time to strike. Grafs.com has Co-Ax presses on sale this week at $289.99. That includes shipping charges (with one flat $7.95 handling charge per order).
4. Grafs.com — NEW Nikon Wind Meter for SmartPhones, $28.99
Here’s a great new gadget for under $30.00. Nikon’s new Spot On™ Ballistic Wind Meter plugs directly into the headphone port on most popular smart phones. The Spot On Wind Meter reads both wind speed and direction and inputs the data directly into Nikon’s free Spot On Ballistics Mobile App (available for iOS and Android). This allows you to quickly determine and calculate wind drift corrections without needing a separate, dedicated wind meter. When not in use, the Nikon device easily fits in a pocket.
Everyone needs a good .22 LR rimfire handgun, and the Browning Buck Mark is a classic. This stainless, bull barrel version is marked down this week to $379.99. That’s a very good price. Buckmarks, with their excellent triggers and great ergonomics, are fun to shoot and VERY accurate. This is a pistol you can keep for a life-time and pass on to your kids. Browning says: “Every Buck Mark starts out as a solid piece of aircraft-grade 7075 aluminum alloy, and then is CNC machined to exacting tolerances. The crisp single-action trigger, hand reamed chamber, target crowned barrel and finely adjustable target sights mean the Buck Mark comes ready for fun straight from the box.”
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In this video, Forum member Erik Cortina shows how to create a custom modified case for use with the Hornady Lock-N-Load Overall Length Gauge (formerly the Stoney Point Tool). While Hornady sells modified cases for many standard cartridges, if you shoot a wildcat such as the 6mm Dasher or .284 Shehane, you’ll need to create a custom modified case*. And even if you shoot a standard cartridge such as the .308 Winchester you can get more consistent measurements if you make a custom modified case from a piece of brass fired in your chamber.
The process is straight-forward. Take a piece of brass fired in your chamber and full-length size it (with about .002″ shoulder bump). Then you need to drill out the primer pocket. Erik uses a mini-lathe for the operation, but this general process can be done with a drill press or other tools. Erik shows how to do this with a 0.290″ HSS (High Speed Steel) drill bit on a mini-lathe. After drilling the hole comes the tricky part — you need to tap the case with the precise 5/16″ x 36 threads per inch (tpi) right-hand thread that matches the male thread on the O.A.L. Gauge. This 5/16″ x 36 tpi tap is pretty uncommon, but you can order it from Amazon.com if you can’t source it locally.
If you use a mini-lathe, Erik suggests loosening the tailstock slightly, so it can float while cutting the threads. Erik also says: “Make sure you get the tap on pretty tight — it’s going to want to spin.” Erik turns the case at about 100 rpm when tapping the threads. Once the case and tap are rigged, the actual tapping process (see video at 6:00) takes only a few seconds. While the mini-lathe makes the tapping process go more quickly, the threading can also be done with other systems.
TIP: Don’t just make one modified case, make three. That gives you one for your range kit, one for your home reloading bench, plus a spare (since you WILL eventually lose or misplace one).
Here’s the Stuff You Need
5/16″-36 TPI Threading Tap
The required thread is somewhat uncommon. You need a 5/16″ – 36 tpi Right Hand Thread Tap. If you can’t find it locally, Amazon.com carries the correct tap. Erik notes: “The 5/16-36 tpi tap is not a common size. I think Hornady did this on purpose to make it more difficult for the average guy to make his own modified cases.”
0.290″ Drill Bit
Erik uses an 0.290″ HSS “L” drill bit. (This “L” Letter Gauge code designates a 0.290″ diameter bit). A close metric equivalent would be 7.3 mm (0.286″). Erik says: “A 9/32″ drill will also work but it will be harder to run the tap in since the hole will be .281″ instead of .290″ with the Letter Gauge L bit.”
Tips for Using O.A.L. Gauge with Modified Case
We’ve noticed that many folks have trouble getting reliable, consistent results when they first start using the Hornady O.A.L. Gauge (formerly the Stoney Point Tool). We’ve found this is usually because they don’t seat the modified case properly and because they don’t use a gentle, consistent method of advancing the bullet until it just kisses the lands.
Here is our suggested procedure for use the O.A.L. Gauge. Following this method we can typically make three of four measurements (with the same bullet), all within .001″ to .0015″. (Yes, we always measure multiple times.)
1. Clean your chamber so there is no build-up of carbon, debris, or lube. Pay particular attention to the shoulder area.
2. Screw the modified case on to the O.A.L. Gauge. Make sure it is seated firmly (and doesn’t spin loose). Note, you may have to re-tighten the modified case after insertion in the chamber.
3. Place your selected bullet so that the ogive (max bullet diameter) is behind the case mouth. This prevents the bullet from “snagging” as you insert the tool in the action.
4. Insert the O.A.L. Gauge into your chamber smoothly. Push a little until you feel resistance. IMPORTANT — You need to ensure that the shoulder of the modified case is seated firmly against the front of your chamber. You may have to wiggle and twist the tool slightly. If you do not have the modified case seated all the way in, you will NOT get a valid measurement.
5. Advance the bullet slowly. (NOTE: This is the most important aspect for consistency!). Push the rod of the O.A.L. tool gently towards the chamber. DON’T shove it hard! Easy does it. Stop when you feel resistance.
6. IMPORTANT. After gently pushing on the rod, give the end of the rod a couple forward taps with your finger. If your bullet was slightly skewed, it may have stopped too far back. Adding a couple extra taps will fix that. If the bullet moves after the taps, then again push gently on the rod. NOT too much! You just want to push the bullet until it just “kisses” the lands and then stops. Do NOT jam the bullet into the rifling. If you do that you will never get consistent results from one measurement to the next.
* For a $15.00 fee, Hornady will make a custom modified case for you if you send two fired pieces of brass. Send fired cases and $15.00 check to: Hornady Manufacturing, Attn: Modified Cases, 108 S. Apollo St., Alda, NE 68810. More Info HERE.
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The USAMU recently published a “how-to” article about bullet sorting. While many of us may sort bullets by base-to-ogive length (and/or weight), the USAMU story explores the “how and why” of sorting bullets by Overall Length (OAL). Read the article highlights below, and make your own decision as to whether OAL sorting is worth the time and effort. Bryan Litz of Applied Ballistics says that sorting by OAL is not a bad idea, but base-to-ogive bullet sorting probably represents a better investment of your time.
Bullet Sorting by Overall Length
We’d like to share a specialized handloading technique which we’ve long found beneficial to our long-range (600 yards and beyond) accuracy. Sorting of bullets for extreme long range (LR) accuracy is not difficult to do, but some background in theory is needed.
Here at USAMU’s Handloading Shop, we only sort individual bullets for the most demanding Long-Range applications and important competitions. Only the most accurate rifles and shooters can fully exploit the benefits of this technique. The basic sorting process involves measuring the Overall Length (OAL) of the bullets, and grouping them in 0.001″ increments. It’s not unusual to find lots of match bullets that vary as much as 0.015″-0.020″ in length throughout the lot, although lots with much less variation are seen as well. Even in bullet lots with 0.015″ OAL variation, the bullet base-to-ogive length will show much less variation. Hence, our basic sort is by bullet OAL. One obvious benefit of sorting is easily seen in the attached photo. The few bullets that are VERY different from the average are culled out, reducing probable fliers.
How does one know what OAL increments to use when sorting? The answer is simple. As each lot of bullets is unique in its OAL distribution, it’s best to sample your bullet lot and see how they are distributed. In the attached photo, you will see a set of loading trays with a strip of masking tape running along the bottom. Each vertical row of holes is numbered in 0.001″ increments corresponding to the bullets’ OAL. A digital caliper makes this task much easier. As each bullet is measured, it is placed in the line of holes for its’ OAL, and gradually, a roughly bell-shaped curve begins to form.
Note that near the center, bullets are much more plentiful than near the edges. At the extreme edges, there are a few that differ markedly from the average, and these make great chronograph or sighting-in fodder. We recommend using a sample of 200 bullets from your lot, and 300 is even better. Some bullet lots are very consistent, with a tall, narrow band of highly-uniform bullets clustered together over just a few thousandths spread. Other lots will show a long, relatively flat curve (less uniform), and you may also see curves with 2 or more “spikes” separated by several 0.001″ OAL increments.
Bullet Sorting (OAL vs. Base-to-Ogive vs. Weight) — Litz Talks
I’m often asked what is a the best measure to sort bullets by, and the answer (to this and many other questions in ballistics) is: it depends.
Choosing to sort by overall length (OAL), base to ogive (BTO), bearing surface, weight, etc. can get overwhelming. Shooters typically look for something they can measure, which shows a variation and sort by that. It’s common for dimensional variations to correlate. For example, bullets which are longer in OAL are typically also shorter in BTO, and have longer noses. All these are symptoms of a bullet that was pushed a little further into the pointing die, or possibly had more than average lube while being swaged. So in essence, if you sort by BTO, you’re measuring one symptom which can indicate a pattern in the bullets shape.
So, the question still stands — what should you measure? You’ll always see more variation in OAL than BTO, so it’s easier to sort by OAL. But sometimes the bullet tips can be jagged and have small burrs which can be misleading. Measuring BTO will result in a lower spread, but is a more direct measure of bullet uniformity.
Then there’s the question of; how much variation is too much, or, how many bins should you sort into? Shooters who see 0.025” variation in BTO may choose to sort into 5 bins of 0.005”. But if you have only 0.005” variation in the box, you’ll still sort into 5 bins of 0.001”. What’s correct? You have to shoot to know. Live fire testing will answer more questions, and answer them more decisively than any amount of discussion on the subject. The test I recommend is to identify bullets on the extreme short end of the spectrum, and some on the extreme long end. Load at least 10 rounds of each, and take turns shooting 5-shot groups with them. If there is a difference, it will be evident. The results of the testing will answer your question of: should I sort based on X, Y, or Z?”
You can read more discussion on this and other similar subjects in the new Ballistics & Bullets board in the Accurateshooter.com forum. Heres a link to the thread which is discussing bullet sorting: Bullet Sorting Thread
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“The overturning moment MW tends to rotate the bullet about an axis, which goes through the CG (center of gravity) and which is perpendicular to the plane of drag….
Ruprecht Nennstiel, a forensic ballistics expert from Wiesbaden, Germany, has authored a great resource about bullet behavior in flight. Nennstiel’s comprehensive article, How Do Bullets Fly, explains all the forces which affect bullet flight including gravity, wind, gyroscopic effects, aerodynamic drag, and lift. Nennstiel even explains the rather arcane Magnus Force and Coriolis Effect which come into play at long ranges. Nennstiel’s remarkable resource contains many useful illustrations plus new experimental observations of bullets fired from small arms, both at short and at long ranges.
Shadowgraph of .308 Winchester Bullet
A convenient index is provided so you can study each particular force in sequence. Writing with clear, precise prose, Nennstiel explains each key factor that affects external ballistics. For starters, we all know that bullets spin when launched from a rifled barrel. But Nennstiel explains in greater detail how this spinning creates gyroscopic stability:
“The overturning moment MW tends to rotate the bullet about an axis, which goes through the CG (center of gravity) and which is perpendicular to the plane of drag, the plane, formed by the velocity vector ‘v’ and the longitudinal axis of the bullet. In the absence of spin, the yaw angle ‘δ’ would grow and the bullet would tumble.
If the bullet has sufficient spin, saying if it rotates fast enough about its axis of form, the gyroscopic effect takes place: the bullet’s longitudinal axis moves into the direction of the overturning moment, perpendicular to the plane of drag. This axis shift however alters the plane of drag, which then rotates about the velocity vector. This movement is called precession or slow mode oscillation.”
Raise Your Ballistic IQ
Though comprehensible to the average reader with some grounding in basic physics, Nennstiel’s work is really the equivalent of a Ph.D thesis in external ballistics. You could easily spend hours reading (and re-reading) all the primary material as well as the detailed FAQ section. But we think it’s worth plowing into How Do Bullets Fly from start to finish. We suggest you bookmark the page for future reference. You can also download the complete article for future reference and offline reading.
In our Shooters’ Forum, a member recently noted that he needed to pull down (disassemble) some ammunition that was loaded incorrectly by one of his shooting buddies. You can use an impact puller to do this task, but if you have more than a dozen rounds or so, you may prefer to use a collet-style bullet puller. These work very quickly and positively, making quick work of big jobs. The efficiency of the collet-style puller is worth the investment if you frequently disassemble ammo. These devices retail for under $25.00 (collets sold separately). Normally, you’ll need a specific collet for each bullet diameter. But collets are not that costly, so this isn’t a big deal, particularly if you only load a few calibers, such as .223, 6mm, and .308.
Hornady and RCBS use different mechanisms to tighten the collet around the bullet. On Hornady’s Cam-Lock Bullet Puller, a lever-arm on the top of the bullet puller serves to tighten the collet around the bullet. Simply rotate the lever from the vertical to the horizontal position to grab the bullet. Lower the ram to remove the case. The bullet will drop out when you return the lever arm to the vertical position. This is demonstrated in the video below:
Hornady Cam-Lock Bullet Puller Demonstrated
Collet bullet-pullers resemble a loading die with a lever or handle on the top. They screw into a standard reloading press. Hornady and RCBS both make collet-style bullet pullers. They use the same basic principle — the device tightens a collet around the bullet, and then the bullet is separated from the case by lowering the press ram. NOTE: Collet pullers may leave small marks on your bullets, unlike impact (kinetic) pullers.*
Like the Hornady tool, the RCBS Bullet Puller employs a collet to grab the bullet. However, the RCBS tool tightens the collet in a different way. The head of the RCBS tool is threaded internally. By rotating the lever arm clockwise in a horizontal circle you squeeze the collet around the bullet. To remove the bullet, after lowering the press ram, simply spin the lever arm back in the opposite direction. The use of the RCBS tool is demonstrated in this video:
RCBS Collet Bullet Puller Demonstrated:
WARNING: When removing bullets from loaded cartridges, always make sure there are no obsructions or debris in your shell-holder or under the loaded round. NEVER engage a primer seating accessory on your press when working with loaded rounds. You can cause a round to discharge by contacting the primer! Also, we recommend you keep your head and torso away from the bullet puller tool at all times.
*By contrast, impact pullers rarely mark bullets, particularly if you put a little bit of foam or paper wadding in the closed end of your impact puller. When dismantling loaded rounds, powder kernels can get trapped in the wadding, so you should remove and replace the wadding before changing to cartridges loaded with a different powder type (assuming you intend to save the powder).
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There is nothing more frustrating (or embarassing) than sending a live round into your expensive new chronograph. As the photo below demonstrates, with most types of chronographs (other than the barrel-hung Magnetospeed), you can fatally injure your expensive chrono if it is not positioned precisely.
When setting up a chrono, we always unload the rifle, remove the bolt and bore-sight to ensure that the path of the bullet is not too low. When bore-sighting visually, set up the rifle securely on the sandbags and look through the bore, breech to muzzle, lining up the barrel with your aim point on the target. Then (during an appropriate cease-fire), walk behind the chronograph. Looking straight back through the “V” formed by the sky-screens, you should be able to see light at the end of the barrel if the gun is positioned correctly. You can also use an in-chamber, laser bore-sighter to confirm the visual boresighting (see photo).
Adjust the height, angle and horizontal position of the chronograph so the bullet will pass through the middle of the “V” below the plastic diffusers, no less than 5″ above the light sensors. We put tape on the front sky-screen supports to make it easier to determine the right height over the light sensors.
Use a Test Backer to Confirm Your Bullet Trajectory
You can put tape on the support rods about 6″ up from the unit. This helps you judge the correct vertical height when setting up your rifle on the bags. Another trick is to hang a sheet of paper from the rear skyscreen and then use a laser boresighter to shine a dot on the paper (with the gun planted steady front and rear). This should give you a good idea (within an inch or so) of the bullet’s actual flight path through the “V” over the light sensors. Of course, when using a laser, never look directly at the laser! Instead shine the laser away from you and see where it appears on the paper.
Alignment of Chronograph Housing
Make sure the chrono housing is parallel to the path of the bullet. Don’t worry if the unit is not parallel to the ground surface. What you want is the bullet to pass over both front and rear sensors at the same height. Don’t try to set the chrono height in reference to the lens of your scope–as it sits 1″ to 2″ above your bore axis. To avoid muzzle blast interference, set your chronograph at least 10 feet from the end of the muzzle (or the distance recommended by the manufacturer).
Rifles with Elevated Iron Sights
All too often rookie AR15 shooters forget that AR sights are positioned roughly 2.4″ above the bore axis (at the top of the front sight blade). If you set your bullet pass-through point using your AR’s front sight, the bullet will actually be traveling 2.4″ lower as it goes through the chrono. That’s why we recommend bore-sighting and setting the bullet travel point about 5-8″ above the base of the sky-screen support shafts. (Or the vertical distance the chronograph maker otherwise recommends). NOTE: You can make the same mistake on a scoped rifle if the scope is set on very tall rings, so the center of the cross-hairs is much higher than the bore axis line.
TARGET AIM POINT: When doing chrono work, we suggest you shoot at a single aiming point no more than 2″ in diameter (on your target paper). Use that aiming point when aligning your chrono with your rifle’s bore. If you use a 2″ bright orange dot, you should be able to see that through the bore at 100 yards. Using a single 2″ target reduces the chance of a screen hit as you shift points of aim. If you shoot at multiple target dots, place them in a vertical line, and bore sight on the lowest dot. Always set your chron height to set safe clearance for the LOWEST target dot, and then work upwards only.
Other Chronograph Tips from Forum Members:
When using a chronograph, I put a strip of masking tape across the far end of the skyscreens about two-thirds of the way up. This gives me a good aiming or bore-sighting reference that’s well away from the pricey bits. I learned that one the hard way. — German Salazar
A very easy and simple tool to help you set up the chronograph is a simple piece of string! Set your gun (unloaded of course) on the rest and sight your target. Tie one end of the string to the rear scope ring or mount, then pull the string along the barrel to simulate the bullet path. With the string showing the bullet’s path, you can then easily set the chronograph’s placement left/right, and up/down. This will also let you set the chrono’s tilt angle and orientation so the sensors are correctly aligned with the bullet path. — Wayne Shaw
If shooting over a chrono from the prone position off a bipod or similar, beware of the muzzle sinking as recoil causes the front of the rifle to drop. I “killed” my first chronograph shooting off a gravel covered firing point where I’d not given enough clearance to start with and an inch or two drop in the muzzle caused a bullet to clip the housing. — Laurie Holland
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If you look at that 5-round group you might think it was shot with a 6 PPC or maybe a 6mmBR. But no, this was done with heavy 180gr Berger Hybrid bullets and the .284 Shehane, an improved version of the .284 Winchester. In fact, this impressive sub-quarter MOA group was shot while fire-forming with a very well-worn barrel!
Here’s a 5-shot 0.191″ group at 100 yards with my .284 Shehane fireforming loads. This barrel has 2200 rounds through it. It had 2000 as a straight .284 Win and then I set it back to .284 Shehane to form brass with. This was the first five rounds through it after I cleaned it after the last match. [The load was] 180 Hybrids with 54.0 grains of H4831 SC.
Ya, I figured why not I had some old barrels laying around so I just chopped 2″ off the back and 1″ off the front and chambered it up as a Shehane. Had 1000 pieces to fireform and didn’t want to do all that on a brand new barrel.
My fireform loads are going 2765 FPS. I have a 29″ barrel also though since it’s a setback. Once you get it formed I would push it faster than that or I wouldn’t even bother with the Shehane. My old straight .284 load at 2890 fps had ES spread in single digits for 10 shots. I figured if I get it up to 2935-2950 fps that will be a point or two saved in a several day match.
Fellow .284 Shehane shooter Erik Cortina notes that the .284 Shehane has a velocity edge over the straight .284 Win because it holds more powder: “The Shehane has more capacity than the .284 Winchester. Ryan is using 54.0 grains simply as a fire-forming load. Typical load for a Shehane is around 57.0 grains of Hodgdon H4831 SC.” By blowing the sidewalls out 0.010″, the .284 Shehane picks up about 3.3 grains of extra case capacity. That enhancement makes a BIG difference. The extra boiler room is enough to drive the 180s at 2900-2950 fps with H4831sc, with long barrels.
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At the request of our readers, we provide select “Deals of the Week”. Every Monday morning we offer our Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.
1. Stocky’s Stocks — Composite Stock with Bedding Block
Here’s a killer deal on a versatile Stocky’s Long Range Stock with aluminum V-block bedding system. For just $199.99, order this for Rem/Rem Clone long actions or short actions, with either narrow or wide (varmint/tactical) barrel channel. This would be a good choice for a varmint rifle. This is also offered with a matte black, tan, or olive baked-on textured finish for $229.97.
2. RCBS — Buy Green, Get Green Rebate
RCBS is running a very attractive Rebate Program currently. If you spend $300.00 on qualifying products you get a $75.00 rebate. Spend $50 and get a $10.00 Rebate. This program is limited to one (1) rebate redemption per calendar year, with a maximum of $75.00. CLICK HERE for more information. NOTE: To qualify, you must supply completed RCBS rebate coupon, original UPC barcodes from package, and original cash register receipt and/or dated, itemized sales invoice.
3. Midsouth — Nosler .308 Match Monster Bullets, $119.99 for 500
Looking for high-quality, name-brand .308-caliber bullets? You won’t beat the price on these Nosler bullets from Midsouth Shooters Supply. Five options are offered: 155 grain, 168 grain, 168 grain (with cannelure), 170 grain, and 190 grain. The 155s and 168s are just $119.99 for FIVE HUNDRED bullets. The 170s cost $131.28/500 while the big 190s cost $137.74/500. Those are insanely good prices, any way you cut it. The price on the 168s works out to just $23.99 per hundred. You could easily pay $40.00 per hundred for bullets of this quality. These are not seconds or blems — the are quality Nosler-made bullets produced for Midsouth’s Match Monster bulk sales program.
4. Sportsman’s Guide — Frankford Arsenal Case Tumbler Kit
For just $69.99, this Frankford Arsenal Kit provides everything you need to clean brass: Vibratory Tumbler, Rotary Media Separator, Bucket, Corn Cob Media (3 lbs.), and Brass Polish. The Case Tumbler holds up to 600 9mm cases or 350 .223 Rem cases. The separator system is generous, with a 3.5-gallon bucket. NOTE: Sportsman’s Guide Buyers Club members can purchase for $62.99.
5. CDNN Sports — Ruger American Ranch Rifle (Tan), $389.99
Here’s a nice little varmint rifle from Ruger with some nice features at a very attractive price, $389.99. This .223 Rem rifle features a 16.5″ hammer-forged barrel barrel threaded 1/2″-28 at the muzzle for brake or suppressor. The action, which features a 70° three-lug bolt, and Picatinny-style scope rail, sits in an aluminum bedding block. The crisp trigger adjusts down to 3 pounds. With a weight (before optics) of 6.1 pounds, this is a handy carry-around varminter.
6. MidwayUSA — Padded Scoped Rifle Case, $24.99
This 48″-long, thickly-padded gun case will hold most tactical-style rifles and hunting rifles. At a fraction of the cost of a big, cumbersome drag bag, this case may be all you need. The heavy duty padding is over 1″ thick on both sides to protect your rifle and optics investment from rough handling. A large pocket will hold a couple boxes of ammo and other accessories. We like this bag much better than the typical gun-store soft cases. It offers much better padding and more room for large scopes. It is on sale this week at MidwayUSA for just $24.99 in four colors: black, tan, OD green, and gray. In addition to the 48″ case shown, 40″ and 44″ versions are available.
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One of our Forum members complained that he wasn’t able to set his primers flush to the rim. He tried a variety of primer tools, yet no matter what he used, the primers still didn’t seat deep enough. He measured his primers, and they were the right thickness, but it seemed like his primer pockets just weren’t deep enough. He was mystified as to the cause of the problem.
Well, our friend Boyd Allen diagnosed the problem. It was the decapping rod. If the rod is adjusted too low (screwed in too far), the base of the full-diameter rod shaft (just above the pin) will contact the inside of the case. That shaft is steel whereas your case is brass, a softer, weaker metal. So, when you run the case up into the die, the shaft can actually stretch the base of the primer pocket outward. Most presses have enough leverage to do this. If you bell the base of the primer pocket outwards, you’ve essentially ruined your case, and there is no way a primer can seat correctly.
The fix is simple. Just make sure to adjust the decapping rod so that the base of the rod shaft does NOT bottom out on the inside of the case. The pin only needs to extend through the flash hole far enough to knock the primer out. The photo shows a Lyman Universal decapping die. But the same thing can happen with any die that has a decapping rod, such as bushing neck-sizing dies, and full-length sizing dies.
Whenever you use a die with a decapping pin for the first time, OR when you move the die to a different press, make sure to check the decapping rod length. And it’s a good idea, with full-length sizing dies, to always re-check the height setting when changing presses.
Lee Universal Decapping Die on SALE for $9.89
Speaking of decapping tools, MidwayUSA has the Lee Universal Decapping Die on sale this month (June, 2010), for just $9.89 (item 136543). There are many situations when you may want to remove primers from fired brass as a separate operation (prior to case sizing). For example, if your rifle brass is dirty, you may want to de-cap before sizing. Or, if you load on a progressive press, things will run much more smoothly if you decap you brass first, in a separate operation. The Lee Universal Decapping Die will work with cartridges from 17 Fireball all the way up to 45-70. However, NOTE that the decapping pin supplied with this Lee die is TOO LARGE for LAPUA 6.5×47, 6BR, 220 Russian, and Norma 6 PPC flash holes. Because the pin diameter is too large for these brass types, you must either turn down the pin, or decap with a different tool for cases with .059″ flash-holes. Otherwise, the Lee Decapping Die works well and it’s a bargain.
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How would you like to “reach out and touch” someone 203 kilometers away (about 110 nautical miles)? Well America’s Navy may soon be able to do exactly that with an amazing new, high-tech weapon system. BAE Systems has developed (and successfully test-fired) an electro-magnetic rail gun that fires a 23-lb projectile at Mach 7 — (about 5300 mph or 7800 fps). This futuristic weapon can send its projectile 110 nautical miles (126 mi / 203 km), five times the range of the big 16″ guns on WWII-era battleships. This railgun has serious “knock-down” power — at Mach 7, that projectile carries a whopping 32 megajoules of energy. BreakingDefense.com says: “23 pounds ain’t heavy. But it sure hurts when it hits you going at seven times the speed of sound.”
Watch Video to See Navy Rail-Gun in Action:
The latest prototype of the railgun developed by defense contractor BAE, in conjunction with the Office of Naval Research, can accelerate a projectile up to Mach 7 within 10 milliseconds. The gun uses no gunpowder to generate propelling force. Compared to an item on a smaller scale, the railgun projectiles resemble crossbow darts, except they deliver such massive Kinetic Energy they don’t need to carry explosive ordnance. The railgun can strike targets 110 nautical miles away.
To prepare a charge, the ship stores electricity in the pulsed power system. Next, an electric pulse is sent to the railgun, creating an electromagnetic force accelerating the projectile. Because of its extreme speed, the projectile eliminates the hazards of storing high explosives in the ship. Each shot costs about $25,000 — but that’s cheap compared to the price of a missile.
“It’s like a flux capacitor,” chief of Naval research Rear Admiral Mathias Winter said in a video posted by Reuters Friday. “You’re sitting here thinking about these next generation and futuristic ideas, and we’ve got scientists who have designed these, and it’s coming to life.”
The Electromagnetic Railgun Innovative Naval Prototype (INP) was initiated in 2005. The goal during Phase I was to produce a proof-of-concept demonstration at 32 mega-joule muzzle energy, develop launcher technology with adequate service life, develop reliable pulsed power technology, and assess component risk reduction for the projectile.
Phase II, which started in 2012, advanced the technology to demonstrate a repeatable-rate fire capability. Thermal-management techniques required for sustained firing rates will be developed for both the launcher system and the pulsed power system. The railgun will begin testing at sea in 2016.
Written by Sierra Bullets Ballistic Technician Duane Siercks
One of the first things new reloaders notice is that load data varies between reloading manuals. The Sierra Bullets Technicians frequently get inquiries asking us to explain why the load data appears to be inconsistent. This article explains five key factors that can influence published load data.
Example of load data variances for two 168 grain bullets:
Here are five reasons why the load data varies:
Basically, the similarities in the .30 caliber 168 grain Match bullets (for example) end with weight and diameter. The bullets likely have dimensional differences such as bearing surface length. Bearing surface has a large effect on pressure and velocity. There are also differences in boat tail, flat base, ogive and over-all lengths, which each help determine the cartridge over-all-length (COAL). With different COAL’s, we can expect changes in pressure and velocity also. In some calibers there are differences in bullet diameter with different bullet manufacturers.
It is also worth noting that bullet manufacturers do not all use the same copper alloy for their jackets. This produces more or less friction that results in load pressures and velocities. The solid copper bullets also vary quite a bit in comparison to a lead core and copper jacketed bullet.
Each gun is unique, even if you are using the same make, model, and caliber. Special consideration should be used to consider that not all firearm chambers are the same either, creating more variables that need consideration. There can be drastic differences in the throat length. This controls the amount of “jump” that a bullet experiences when the cartridge is fired.
Within normal manufacturing tolerances, you can see some variation in a given powders burn rate between different lots of the same powder. So naturally when two different Manuals are produced, it would be doubtful that the same lots would be tested.
The Cartridge Cases
New cases are almost always near minimum specs in dimension. A load fired in a new case would likely have slightly more pressure that when fired in a re-sized case. This would certainly be true if we were loading into fire-formed cases that have had minimal re-sizing done. Fired cases that are full length resized most of the time be slightly larger than the new unfired cases. This gives you differences in case capacity. The same powder charge placed within a new case and a full length resized case will produce different pressure levels and probably different velocities.
Temperature can cause pressure increases or decreases. Hot temperatures tend to cause pressures to increase, while cold temperatures will usually do the opposite. Humidity and altitude can impact pressures and velocities likewise.
As you can see, an amazing number of variables effect any load combination. With the differences in the manuals, you’re just seeing firsthand examples of what took place when the data was collected with that particular set of components and firearm. Think of a reloading manual as a report. In essence, a reloading manual says, “We tried this particular component combination, and these are the results we obtained.”
Remember that you may or may not reach the same maximum load safely. There is no “one load fits all bullets.” The minimum load data offers a safe place to start. The maximum load data listed should always be regarded as a safety guideline and not necessarily a goal! Your gun should shoot accurately without breaching the maximum load data. The best advice is: always start low and work your load up!
If you have questions about variances in load data or other reloading questions, please call our ballistic technicians at 1-800-223-8799 or send us an email at sierra [at] sierrabullets.com.
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